We should go back to the moon and build a giant sling shot
to shoot giant rocks into deep space for the purpose of
contacting life on other planets. Much cheaper than robot
space probes. We could hire the best spray paint graffiti artists
in the world to paint cryptic and annoying messages on
the rocks,
announcing to the universe our presence. In a pinch, we could
also use the sling shot to shoot down the alien spacecraft that
will inevitably follow the path of the rocks or decode the
cryptic messages and come to earth to destroy who it is that's
being such a pain in the ass. I think we need this kind of adversity
if we are going to amount to anything.

Not a bad idea, considering that a railgun projectile is not *that* much slower than c, in the cosmic scheme of things. It will still take millennia before it gets anywhere. As far as the content goes, is graffiti any less cryptic or annoying than the Little Richard tune sent on the Voyager record?

Yeah, I thought about the 'speed' issue....but then realized, that's the
beauty of this thing. We will be long dead and gone by the time any
thing happens. Along with high taxes and a global environment in
turmoil, we'll be passing along a little present to future
generations.....something to look forward to.....an alien
invasion would be our legacy.

if we're going to be throwing these rocks away, can we put cameras and sensors on them?
Expand out sphere of observation outward from this system at close to C? There are about 100 stars within 20 ly of Earth. If you build a good enough transit system infracture here we could get things really moving.... really long rail guns powered by solar energy or quantum flux...
Solar sails for the inner system... I think that if we can scale up things from the technical roots we have now somebody somewhere is going to notice us sniffing around the place, poking our noses into the wrong places and generally stinking the place up with our monkey odors....
some advance warning would be really nice....

The addition of cameras and sensors will drive the
cost up.....and complicate the system...it's only intent
is to bother someone out there...a proverbial 'thumbing
our nose at the universe' kind of thing. By the
time these reach anything of any relavance, we will
have been dead several centuries. Who cares about
warnings?

It wouldn't be too expensive to stick a copy of the Voyager
(or was it Pioneer?) record plate on each rock, the one
which shows where Earth is in relation to various nearby
pulsars. One presumes They will have enough celestial
mechanics foo to figure out where the rock came from, but
why take chances?

Of course, come the Revolution Esc-d Singularity, it won't be
any more expensive or complicated to have a little robot
probe grow on each rock as it goes outward.

Wait. While we're putting cameras and sensors on rocks, can we put people on them too? YEA! We can put people INSIDE OF THEM...and we could even put an engine on it so it could travel on its own. THAT would be useful too! Wait a minute...big chunky thing with cameras, sensors, people inside, and an engine flying around in space...sounds familiar...

The sheer force of acceleration from zero to a fraction of c in less than a second using a device of this nature would create more than enough gravititational force to reduce a human to a quivering blob of jelly.